In what could be a stepping stone towards customised babies, researchers have identified a key mechanism by which environmental factors influence traits like our height, skin colour and intelligence.

They believe that by identifying a key gene for each trait and how it is affected epigenetically (by the environment), it is potentially possible to influence the degree of its expression - and so create variation in how specific traits are expressed.

"It's a discovery that completely changes our understanding of how human variation comes to be," said one of the lead researchers, professor Ehab Abouheif of the McGill University.

So many human traits, whether they are intelligence, height, or vulnerability to diseases such as cancer, exist along a continuum.

"If, as we believe this epigenetic mechanism applies to a key gene in each area, the change is so enormous that it's hard to even imagine right now how it will influence research in everything from health to cognitive development to farming," Abouheif added.

A McGill University team led by professors Moshe Szyf and Ehab Abouheif arrived at this conclusion by conducting epigenetic experiments on Florida carpenter ants.

By increasing the degree of DNA methylation (a biochemical process that controls the expression of certain genes) of a gene called Egfr involved in controlling growth, they were able to create a spectrum of worker ant sizes despite the lack of genetic difference between one ant and the next.

Essentially, the researchers found that the more methylated the gene, the larger the size of the ants.

"By modifying the methylation of one particular gene, that affects others, in this case the Egfr gene, we could affect all the other genes involved in cellular growth," said study co-author Sebastian Alvarado from the McGill.

"We were working with ants, but it was a bit like discovering that we could create shorter or taller human beings," Alvarado said.